Air compressor



Nov. 12, 1935. c. w. H.. JoHNsgroN AIR COMPRESSOR Filed June 16, 1934 fw. /v

f Jr ,o 9 z n s 441 ya., ,9 .nv 5 0 z 4 w /m M wm n M J @am Patented Nov. 12, '1935 UNITED STATES PATENT OFFICE.

6- Claims.

This invention relates to new and useful improvements in air compressors.

One object of the invention is to provide an improved air compressor which is arranged to be operated by the passage of vehicles thereover.

Another objectA of the invention is to provide an improved air compressor which is located in the path of vehicles, whereby said vehicles will operate the compressor to compress and store air.

-A particular object of the invention is to provide an air compressor including a pivoted treadle on its upper surface coacting with a :stationary member to compress air therebetween upon depression of said treadle.

A further object of the invention is to provide means for automatically locking the compressor against operation when the air in the storage tank reaches a predetermined pressure.

Another object of the invention is to provide an air compressor having a pair of tanks embedded in the ground and pivoted treadles arranged thereabove to coact with the tanks to cornpress air therebetween; the tanks thereby being out of the way and the treadles projecting slightly' above the ground in order that ther vehicles passing thereover will depress said treadles and compress the air between said treadles and the tanks.

A still further object ofthe invention is to provide an air compressor having two tanks each of' which is provided with a pivoted treadle coacting therewith to compress air, the tanks being arranged so that the air compressed by both treadles will first be introduced intol one of the tanksV and when the pressure in thisl tank reaches a predetermined point, thenA air is permitted to enter the second tank.

A construction designed to carry out the invention will be hereinafter described, together with other features of the invention.

The invention will be more readily understood from a reading of the following specification and by reference to the accompanying drawing, Vin which an example. of the invention 1s shown, and

wherein:

Figure 1 is an end View partly in elevation andA Figure 6 is an enlarged sectional View of one of the treadle valves, and,

Figure '7. is an, enlarged sectional view of the front portion of one of the compressors showing the air seal between the treadle and the 5 tank.

In the drawing the numeral l0 designates a rectangular shallow casing which is embedded in the drive-way of a service station or any other place along which vehicles travel where it may 10 be desired to use the device. The top of the casing is open and is ush with the drive. The drive may be inclined so as to provide an approach for the device and also to prevent water flowing into the casing. The casing may beY pro- 15 vided with a suitable drain trap (not shown) A pair of compressors consisting of rectangular storage tanks II' and I2A are disposed. transversely in the casing'. These tanks are set on blocks or cross members i3' in the casing and are suitably secured 20 therein.

Each tankI is provided with an airY compressing member or treadle I4 and I5', each of which is pivoted on a longitudinal shaft i6. These shafts are journaled in ears I6 which are mounted 25 on the rear of the tanks. It is notedv in Figures 2 and 3, that the treadles are provided with depending marginal flanges or aprons 39 which surround the upper portion of the tanks when the treadles are in an elevated position. The treadles 30 are also provided with oppositely inclined treads which cover the top of the tanks. A suitable packing ring I'i is mounted along the upper edge of the tank; This ring is fastened at its lower edge to the tank in such a manner that its upper 35 edge is free to be displaced against the depending apron of the treadle. Attention is called to Figure 7, wherein it isf seen that the air will exert its pressure behind the ring at its top and force the same against the apron to effectively 40 form an air-tight seal.

Gear racks l8- are disposed on the adjacent aprons ofthe treadles so that they mesh with each other, whereby the two treadles move as a unit. The treadle I4 is provided with a suitable 45 coiled spring I9 to hold said treadle in an elevated position. The upper end of the spring engages under alug 20A which extends outwardly at one side from the bottom of the apron 39 of the treadle Hl. treadles is limited by the lug engaging the lower end of a bolt 2l which is threaded through a plate extending inwardly from the top of the casing.

A cylinder 23 is disposed along one side of the 55 The upward movement of the 50 tank II near its bottom, and is connected at one end to the tank by a pipe 24. A piston 25 is mounted to reciprocate in the cylinder and has its rod 26 extending through the front end of said cylinder. A coiled spring 21 surrounds the rod and is conned between the front end of the cylinder and the piston. The forward end of the rod 26 is connected to a pivoted latch 28, whereby reciprocation of the piston will swing said latch.

The tops of the treadles are provided with air inlet check valves 29 preferably of the ball type but any valve suitable for the purpose may be used. A sump 3|) is provided in the top of the tank for receiving the valve when the treadle is in its lowered position. In Figure 6, I have shown a cap 3l which may be mounted above the valves if so desired. The caps prevent dirt and other extraneous matter entering the treadles and interfering withv the operation thereof.

The tanks are provided with suitable air inlet check valves 32 and 33 mounted in their tops. The valves shown are of the plunger type but any Valve suitable for the purpose may be used.

Attention is called to Figure 2 wherein it is noted that the valve 33 opens directly into the tank I2. The valve 32 is'also connected by a pipe 34 to the tank I2. Thus it is seen that all the air trapped and compressed between the spring 35 of a check valve 3S is overcome and the compressed air is allowed to pass through a pipe 31 connecting the two tanks, into the tank II.

Now upon each successive operation of the treadles, the air will enter the tank I2 and after reaching a certain pressure, will then pass into the tank I I; after the air in the tank I I reaches a predetermined pressure the tension of the spring 21 in the cylinder is overcome. This forces the piston 25 to the forward end of the cylinder 23 and the latch 28 is swung into the path of the lug 20. Upon the next down stroke of the treadles the latch will engage the lug and prevent upward movement of the treadles. In case too high a pressure is built up in the tank I I, a safety valve 38 is provided in its rear side.

Outlet pipes 4J and 4I lead from the tanks II and I2 respectively and connect to a main air supply line 42. A two way valve 43 of the usual type is connected at the intersection of the pipes 40 and 4I and the line 42, whereby the passage of air from either pipe to said line is controlled.

When the pressure in the tank II has been lowered sufliciently, the spring 21 will return the piston 25 to the rear end of the cylinder 23 and the latch will be disengaged from the lug 29, whereby the treadles will again rise to their elevated position and be ready for operation. It is to be understood that the invention is not limited to two compressors or two tanks, as the The operation of the device is as follows.

"When the treadles are in their elevated position as shown in Figure 1, and the front Wheels of a vehicle pass thereover, the weight of the said vehicle will depress the treadles. This depression will force air that is trapped between the treadles and the top of the tanks through valves 5 32 and 33. The air that passes through the valve 33 is admitted directly into the tank I2, while the air that passes through the valve 32 is led by a pipe 34 into the same tank I2. The idea is that the tank I2 will be filled rst and the 10 air compressed therein until a sufficient predetermined pressure is reached. This depression also compresses a coil spring I9 and when the front wheels have passed over and off the treadles the same is forced upwardly due to the action 15 of the said spring. The tread of the treadles are provided with air inlet valves 29 in order that air will be admitted beneath the treads into the treadles on the upstroke. The coil spring I9 returns the treadles to their elevated positions rather quickly. When the back wheels of the vehicle pass onto the treadles the same action is repeated as has been described for the front wheels.

After suiiicient operation, the pre-determined pressure is reached in the tank I2. This pressure will then operate the valve 35 and air is then admitted to the tank II. The tank II will then be filled upon a continued operation of the treadles and when a predetermined pressure is reached, this air pressure will force the piston 25 forwardly under tension of the spring whereby the latch 28 is swung into the path of the lug 20 on the treadle I4. Upon the next downward movement of the treadles the latch will engage said lug and prevent the rise of said treadles.

The valve 43 controls the air entering the main supply line 42 from either of the pipes 40 and 4I. It is obvious that the valve may if de- 40 sired be entirely closed ol. The device is simple in construction and depends only on the vehicles passing thereover for operation. It is again pointed out that the invention is not to be limited to two tanks, as efficient operation may be had 45 with a single tank.

The description which has been given recites more or less detail of a particular embodiment of the invention, which is set forth as new and useful; however, I desire it understood that the 50 invention is not limited to such exact details of construction, because it is manifest that changes and modications may be made, Within the scope of the. appended claims, without departing from the spirit of the invention.

What I claim and desire to secure by Letters Patent, is:

1. An air compressor comprising, a tank, a treadle arranged to be operated Iby vehicles pass- 60 ing thereover and coacting with said tank to compress air therebetween, means for admitting air between said treadle and tank, the tank constituting a storage chamber for the compressed air, and means for conducting the compressed 65. air from between said treadle and tank to the tank.

2. An air compressor comprising, a tank, a treadle arranged to be operated by vehicles pass-r ing thereover and coacting with said tank to compress air therebetween, means for admitting air between said treadle and tank, the tank constituting a storage chamber for the compressed air, and means for conducting the compressed air from between said treadle and tank to the tank, and means for locking said treadle in an inoperative position.

3. `An air compressor comprising, a tank, a

,treadle arranged to be operated by vehicles passing thereover and coacting with said tank to compress airtherebetween, check valves in the treadle for admitting air between said treadle and tank, the tank comprising a storage chamber for the compressed air, and valves in the tank arranged to be operated by compressed air admitting the compressed air from between said treadle and tanks to the tank. Y

4. Ari air compressor comprising, a pair of storage tanks, a treadle coacting with each tank to compress air therebetween and arranged to be operated by vehicles passing thereover, check Valves for admitting air between between each treadle and tank, means for conducting the air compressed by both treadles to one of the tanks, and a closed connection between the tanks arranged to be opened when the air in the first tank reaches a predetermined pressure, whereby air is then conducted to the second tank.

5. An air compressor comprising, a stationary member, a treadle pivoted to the member and arranged to swing thereover and having an air admitting opening therein, the treadle being arranged to be Vdepressed by vehicles passing thereover, the space between the treadle and member forming an air compressing chamber wherein the air within said chamber is compressed when the treadle is depressed, and a storage chamber for the compressed air.

6. An air compressor comprising, a stationary member, aA treadle pivoted to the member and arranged to swing thereover and having an air admitting opening therein, the treadle being arranged to be depressed by vehicles passing thereover, the space between the treadle and member forming an air compressing chamber wherein the air Within said chamber is compressed when the treadle is depressed, a storage chamber for the compressed air, and means for locking said treadle in an inoperative position.

CLARENCE W. H. JOHNSTON. 

